Recent observations that certain myeloid colony-stimulating factors (CSF) induce macrophages to secrete biologically important molecules justifies an in depth investigation of the role of CSF in regulation of the inflammatory and immunological functions of macrophages. This investigation is proposed in an attempt to more clearly define factors influencing macrophage functions in both chronic and acute inflammatory responses. Highly purified CSF will be prepared from several murine cell lines (L929, EL-4, and P388-D1) which produce CSF molecules similar if not identical to those produced by different cell types in vivo. Additionally, as potential aids for expediting purification and as research tools, antisera specific for these different CSF preparations will be raised in rabbits. These different CSF preparations will be assayed for their capacities to stimulate macrophage secretion. Secretory products to be measured are interferon, lymphocyte activating factor (interleukin 1), fibroblast activating factor and superoxide radical. All of these factors are believed to play important roles in both the beneficial and pathological events associated with macrophage activation. Additionally attempts will be made to determine the responsiveness of different macrophage populations and subpopulations to the stimulatory effects of CSF. Macrophage populations to be assayed will be taken from normal and exudate peritoneal washes, liver, spleen and thymus. These cell preparations will be further divided into Ia-antigen positive and negative subpopulations. Further density-based fractionation will be employed to determine the relationship between secreting cells and those cells proliferating in response to CSF. CSF-induced macrophage secretion will be investigated with particular emphasis being placed on regulatory interactions acting to influence secretion. Finally, the purified CSF and their specific antisera will be utilized to probe the involvement of CSF in the course of primary in vitro immune responses.